The present invention relates to an energy conservation system that is installed on an earth-moving loading machine having a boom assembly.
Wheel loaders and hydraulic excavators are typical earth-moving loading machines machines that are designed and constructed to dig, raise, and/or carry heavy payloads comprised of dirt, rocks, sand, other natural earth components, and/or construction materials. Such earth-moving loading machines commonly have a boom assembly that operably connects the base of the machine to a bucket or shovel. The boom assembly is raised and lowered by hydraulic cylinders which are controlled by a series of hydraulic valves. Energy is provided to the hydraulic cylinders by a diesel-powered or electric motor.
As mentioned, one common earth-moving loading machine is a hydraulic excavator. A hydraulic excavator has an open bucket mounted to the end of a boom assembly best described as an articulated arm having a boom portion and a stick portion. The hydraulic excavator is commonly used for digging materials from loading faces or shallow holes and trenches. A hydraulic excavator is one of the more versatile loading machines in that it can be configured as a front shovel or as a backhoe.
Another common earth-moving loading machine is a wheel loader. A wheel loader has a scoop-like bucket mounted to a boom assembly. This earth-moving loading machine is designed to lift and carry dirt, rocks, sand, and other construction materials. In practice, a wheel loader is commonly used to move materials from the ground, loading them into a truck, conveyor hopper, or storage bin.
In operation, an earth-moving loading machine cycles through a series of operations to dig, raise, and transfer a load. First, the operator of the loading machine lowers the bucket and then pushes and curls the bucket into a pile of fractured earth or material. The bucket is manipulated by the operator to obtain a full payload. Using the machine""s hydraulic power, the boom hoist cylinders are filled, raising the boom assembly and bucket to the desired height, which typically is a height sufficient to clear the side rail of the truck being loaded. The operator then moves the bucket to the desired position (for example, adjacent a truck) and dumps the contents of the payload. The boom assembly is returned to a position for acquiring another payload. The operator opens the hydraulic control valves, allowing the hydraulic fluid to escape from the boom hoist cylinders, and causing the boom assembly and bucket to return to the lowered position under the force of their own weight. This cycle is then repeated.
For a fuller understanding of the hydraulic system of an earth-moving loading machine, see, for example, U.S. Pat. No. 5,855,159 issued to Yoshida and assigned to Komatsu, Ltd. of Japan; U.S. Pat. No. 5,471,808 issued to Lech and assigned to the Case Corporation of Racine, Wis.; and U.S. Pat. No. 5,103,253 issued to Kobayashi et al. and assigned to Kubota, Ltd. of Osaka, Japan. Each of these patents is incorporated herein by reference.
Clearly, the hydraulic forces required to raise the boom assembly are substantial. Hydraulic systems of the prior art, however, are extremely inefficient. Specifically, every time the machine dumps its payload from the raised position, the operator opens a hydraulic valve, releasing the hydraulic fluid and allowing it to flow back to the associated hydraulic tank, thereby lowering the boom assembly. In so doing, the potential energy stored through the raising of the boom assembly is lost.
It is therefore a paramount object of the present invention to provide a earth-moving loading machine that provides for more efficient raising and lowering of the boom assembly and bucket.
This and other objects and advantages of the present invention will become apparent upon a reading of the following description.
The energy conservation system of the present invention is preferably comprised of one or more pressurized gaseous pistons that extend from the front of the frame of an earth-moving loading machine to the boom assembly. Such a piston essentially acts as a spring that biases the boom assembly to a raised position. Thus, a portion of the weight of the boom assembly and associated payload is always supported by the piston. Alone, this piston does not provide sufficient force to maintain the boom assembly in a raised position. However, the use of such a piston reduces the forces that need to be supplied by the hydraulic boom hoist cylinders to raise the boom assembly. Thus, operating at the same cycle speeds as a prior art loading machine requires substantially less hydraulic horsepower. Or, if the same amount of hydraulic horsepower is provided. cycle times can be reduced and output increased because of the decreased time required to raise the boom assembly. The incorporation of the energy conservation system of the present invention into a loading machine also allows for a more controlled lowering of the boom assembly. Finally, the lowering of the boom assembly stores a portion of the potential energy by compressing the gaseous contents of the piston back to essentially the same pressure that existed prior to the raising of the boom assembly, thereby conserving energy.